Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.53	8.608%	$235.1689	$235.17	$235.15	$235.20
Purchase #2	$250.83	12.390%	$281.9078	$281.91	$281.90	$281.90
Purchase #3	$76.51	5.503%	$80.7203	$80.72	$80.70	$80.70
Purchase #4	$142.83	3.855%	$148.3361	$148.34	$148.35	$148.30
Purchase #5	$40.90	5.862%	$43.2976	$43.30	$43.30	$43.30
Purchase #6	$29.86	6.418%	$31.7764	$31.78	$31.80	$31.80
Purchase #7	$50.50	3.511%	$52.2731	$52.27	$52.25	$52.30
7 purchase totals =	$807.96		$873.4802	$873.49	$873.45	$873.50